Critics of the deal to cap Iran's nuclear programme say it repeats mistakes made with North Korea, but analysts say there is little to suggest Tehran will follow Pyongyang's path of broken promises to a nuclear bomb.

Under the agreement sealed in Geneva on Sunday, Iran undertook to brake its nuclear drive for the next six months in exchange for limited sanctions relief.

Republican dissenters in the US Congress warned that Tehran was borrowing from Pyongyang's well-worn playbook, buying time and financial largesse with false promises that ultimately led to North Korea's first nuclear test in 2006.

On the surface there are similarities that go beyond Iran and North Korea's joint billing with Iraq in former US president George W. Bush's "axis of evil".

Albeit to varying degrees, both are autocratic, diplomatically isolated, sanctions-laden nations with a shared history of long-term enmity with the United States and a desire for nuclear leverage.

In North Korea's case, a series of aid-for-denuclearisation agreements over the past 20 years have fallen apart, and Pyongyang is openly developing weapons on all fronts following its third and largest nuclear test in February this year.

But many analysts believe suggestions that Iran will inevitably follow the same path ignore key social, structural and geopolitical differences.

The core difference for Stephan Haggard, a North Korea expert at the University of California, is the "observable shift" in Iran's government with the election in June of Hassan Rouhani as president.

Rouhani's reputation as a moderate, and his desire to move from confrontation to engagement, made the negotiated deal with Tehran worth risking, said Haggard.

"Nothing similar is visible in North Korea" he added.

Since the young Kim Jong-Un came to power in December 2011 -- the third generation of the Kim dynasty that has ruled the country with an iron fist since the 1950s -- North Korea has enshrined its nuclear statehood in its constitution and vowed it will never negotiate its atomic weapons away.

Iran's economic stake is also far greater than any taken by North Korea in its nuclear agreements -- a fact that experts say should help bind Tehran to the terms of the Geneva deal.

Sanctions have ravaged an Iranian economy that was previously relatively well-integrated with the international trading system, in a country that has a well-educated middle class and memories of far better times in the recent past.

The North Korean economy has been isolated and moribund for decades and the Kim regime has shown it can maintain its grip on power while imposing enormous economic hardship on its harshly controlled people.

"The cost and benefit decision presented to Tehran was and is very clear," said Paul Carroll, programme director at the Ploughshares Fund, a US-based global security foundation.

"The North Korea security calculus is tilted the other way -- it's worth the pain to get a weapon," Carroll said.

"And also Iran lacks the kind of support the North has traditionally got from China, that allowed Pyongyang to feel 'this hurts, but Beijing has our back'," he added.

Critics of the Geneva deal point to the 1994 "Agreed Framework" that Bill Clinton's US administration signed with North Korea.

At that time, the similarities with Iran were more striking. North Korea, like Iran now, had yet to conduct a nuclear test and was still a member of the non-proliferation treaty (NPT).

The 1994 agreement eventually broke down amid mutual accusations of non-compliance, but non-proliferation experts say the Geneva accord -- even as an interim deal -- is stronger for its tough inspection regime.

Iran agreed to daily site inspections by experts from the UN nuclear watchdog IAEA, which will also monitor implementation of the agreement.

"In the case of North Korea, the IAEA had limited access to just one facility," said Daryl Kimball, executive director of the Arms Control Association.

"Iran, by contrast, has committed to very intrusive inspections at a wider range of facilities across its entire nuclear landscape," Kimball said.

If there is no reason for Iran to follow North Korea's nuclear path, most experts also believe it is unlikely that the Geneva deal might trigger a similar agreement with Pyongyang.

Unlike Iran, North Korea has a nuclear bomb, and the Kim regime sees a nuclear deterrent as the guarantor of its survival.

"North Korea is well aware of the difference between its own case and the Iranian case and will not give up its nuclear programme," said Paik Hak-Soon of the Sejong Institute think tank in Seoul.